The invention relates to a mechanical and electrical connection element for the use in low, medium and high voltage, for circuit breakers, reclosers and

switchgears.

Electrical connections of current carrying parts need a certain force onto the contact surfaces, in order to realize a safe mechanical contact, as well as an optimal electrical contact with minimum transition resistance , and this force needs to be reliable over time regardless e.g. of mechanical vibrations and temperature cycles. Known ways of realization of electrical connections of this kind are e.g. connections with screws, nuts and spring washers.

The disadvantage of using a screw and a spring washer is, that the end of the screw extends to the outside of the assembly. This can result in electrical

problems due to the relatively sharp edges of the head of the screw. Further, especially for outdoor applications, it is disadvantageous to have many parts, transitions between parts and uneven surfaces with edges, where pollution and humidity can adhere, because of increased corrosion. This can reduce the

dielectric and/or the conductivity performance of the switchgear and can also initiate thermal losses at transition restistances.

An already good embodiment, to realize a good electrical and mechanical contacting is disclosed by the application of a stretched bolt between both contacting parts, like known from the EP 3 029 777 A1 , which is already advantageous for a number of applications. But in this construction, both sides of the stretch-bolt end in a terminal part at one side, and in a connector part at the other side.

This is advantageous for an number of applications.

The aforesaid design requires a certain length for two threaded connections, the object of the invention is, to overcome the aforesaid disadvantage, the aforesaid design requires a certain length for two threaded connections.

The above mentioned object is fulfilled by the inventive feature combination of claim 1 .

Further embodiments are given by the further dependend claims.

So the basic invention is, that the connecting system comprises a stretch-bolt function, which is integrated in one of the current carrying parts, and that the stretch bolt feature is provided with a male screw thread at the extending end, which has to be screwed into a female threaded hole of the other current carrying part.

By the invention it is proposed to integrate the stretched bolt function into one of the current carrying parts. So, the totally required length is shorter. This can also result in a reduced mass.

Furthermore, the number of parts is reduced.

Integration means here that the bolt function is either realized as a feature of one current carrying part, i.e. the bolt is not assembled or linked to the current carrying part, but e.g. machined together wit the current carrying part from the same raw part, or realized by a permanent joint of the stretched bolt with the current carrying part e.g. by soldering, hard soldering, welding friction welding, heat shrinking or alike.

In a further advantageous embodiment, the in the concerning current carrying part integrated end of the stretch-bolt is integrally bonded to the aforesaid current carrying part at the bottom of a stud hole, and that the inner diameter of that stud hole is bigger than the outer diameter of the stretch bolt.

The material for the integrated stretch bolt has to be chosen according to the needs of current carrying capability and to the needs of the mechanical strength of the threaded connection.

Current carrying parts are usually made of copper or aluminium. Screws and threaded bolts are also regularly being made of these materials. It will have to be considered that the specific mechanical strength of these bolts will be lower compared e.g. to threaded bolts made of steel, but this can be compensated by increasing the diameter of the integrated stretch bolt.

In a further advantageous embodiment, the stretch bolt as well as at least one of the current carrying parts is made of aluminum or copper.

The electrical conductivity of aluminium and copper can slightly be reduced, when the materials are adjusted for high mechanical strength. This can be considered in the overall design of the low, medium or high voltage equipment.

Especially for outdoor applications, the current carrying parts usually have quite some margin regarding current carrying capability, so that it would not be required to increase e.g. the diameter of the current carrying parts. ln a further advantageous embodiment the second current carrying part is partly embedded into insulation material.

A last embodiment is, that the first current carrying part is a terminal, of a vacuum interrupter, which is embedded into said insulation material.

Figure 1 shows a first current carrying part 1 , a second current carrying part 2 and a stretch bolt 3, like already published in the EP 3 029 777 A1 as state of the art.

Figure 2 shows a first current carrying part 4 with an integrated stretch bolt, and a second current carrying part 2. During assembly, part 4 is rotated against part 2 like a screw until the integrated bolt is sufficiently stretched.

An advantageous embodiment of this invention is the application to a pole part, where the second current carrying part 4 is a terminal of said pole part, that is partly embedded into insulation material. The first current carrying part 1 can then be a terminal of a vacuum interrupter embedded into said insulation material.